EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate

Simone Cesca1, Carla Valenzuela Malebrán1,2, José Ángel López-Comino2,3,4, Timothy Davis1,2, Carlos Tassara5, Onno Oncken1, and Torsten Dahm1
Simone Cesca et al.
  • 1GFZ German Research Centre for Geosciences Potsdam, Section 2.1, Potsdam, Germany (
  • 2Institute of Earth and Environmental Sciences, University of Potsdam, Potsdam, Germany
  • 3Instituto Andaluz de Geofísica, Universidad de Granada, Granada, Spain
  • 4Departamento de Física Teórica y del Cosmos, Universidad de Granada, Granada, Spain
  • 5Universidad Nacional Arturo Prat, Iquique, Chile

A complex seismic sequence took place in 2014 at the Juan Fernández microplate, a small microplate located between Pacific, Nazca and Antarctica plates. Despite the remoteness of the study region and the lack of local data, we were able to resolve earthquake source parameters and to reconstruct the complex seismic sequence, by using modern waveform-based seismological techniques. The sequence started with an exceptional Mw 7.1-6.7 thrust – strike slip earthquake doublet, the first subevent being the largest earthquake ever recorded in the region and one of the few rare thrust earthquakes in a region otherwise characterized by normal faulting and strike slip earthquakes. The joint analysis of seismicity and focal mechanisms suggest the activation of E-W and NE-SW faults or of an internal curved pseudofault, which is formed in response to the microplate rotation, with alternation of thrust and strike-slip earthquakes. Seismicity migrated Northward in its final phase, towards the microplate edge, where a second doublet with uneven focal mechanisms occurred. The sequence rupture kinematics is well explained by Coulomb stress changes imparted by the first subevent. Our analysis show that compressional stresses, which have been mapped at the northern boundary of the microplate, but never accompanied by large thrust earthquakes, can be accommodated by the rare occurrence of large, impulsive, shallow thrust earthquakes, with a considerable tsunamigenic potential.

How to cite: Cesca, S., Valenzuela Malebrán, C., López-Comino, J. Á., Davis, T., Tassara, C., Oncken, O., and Dahm, T.: Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1119,, 2021.

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